Mixed lines crossed fields oscillator or amplifier



March 30; 1965 D. A. WILBUR 3,176,183

MIXED LINES CROSSED FIELDS OSCILLATQR 0R AMPLIFIER Filed Oct. 28. 1960 :s Sheets-Sheet 1 /n venfor Donald A. Wilbur b /Ma. 0%

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March 30, 1965 D. A. WILBUR MIXED LINES GROSSED FIELDS OSCILLATOR OR AMPLIFIER Fil8d 0012. 28. 1960 3 Sheets-Sheet 2 Fig. 9.

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- March 38, 1965 MIXED LINES CROSSED FIELDS OSCILLATOR OR AMPLIFIER Filed 061'. 28. 1960 D. A. WILBU R 3 Sheets-Sheet 3 Fig. /8.

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t d States Patmt 3,176,188 A MIXED LINES CROSSED FiELDS OSCHJLATOR R AMPLIFIER Donald A. Wilbur, vScotia, N.Y., assignor to General Electric Company, a corporation of New York Filed Oct. 28, 1960, Ser. No. 65,716 12 Claims. (Q1. 31539.69)

, This invention relates to a magnetron tube apparatus and more particularly to innovations facilitating mode stabilization in the operation of magnetrons.

In general, magnetrons comprise an anode block in which a plurality of resonant cavities are formed in symmetrical arrangement about its circumference and which are separated 'byv partitions called segments or vanes extending from the inner periphery of the anode to an inner radius to terminate in anode tips.

"ice,

, 2 over that of other modes and operation of magnetrons in the pi-mode is, therefore, frequently preferred. However, even stabilization of magnetron operation in the pi-mode according to strapped structures heretofore known, presents considerable difficulty, particularly under high or varying load conditions. i Stability of magnetrons and suppression of undesirable modes have been even further accomplished by introducing an assyrnmetry for these undesirable modes into the strapping system. This may be achieved by strapping the magnetron over less than it entire anode circumference, thus leaving a portion or portions of it unstrapped- In this way, for a desirable pi-mode operation, the resonant frequency and phase-shift-per-anode- A cathode is disposed longitudinally along the tube axis and is' equally spaced from the anode tips to form an interelectrode interaction region therebetween. A positive potential applied to the anode with respect to the cathode establishes a direct electric field between these electrodes and a direct magnetic field is established along the mag-' netron axis. Thus,- crossed electric and magnetic fields exist in the interaction region between cathode and anode. In the operation of the magnetron, electrons are emitted from the cathode to form a beam which travels around the cathode in the interaction region and an electromagnetic wave is propagated along the magnetron anode as a slow Wave structure. Under the influence of substantially constant electric and magnetic fields, the beam moves at substantially constant velocity. Effective transfer of energy from the beam to the electromagnetic wave is achieved wherein the waveis propagated uniformly about the magnetron and is in synchronism with the beam. That is, the two travel at the same angular pod and unstrapped portions of the anode.

vane for the desired frequency are the same for both strapped and unstrap'ped portions of the anode while for all other modes, these parameters are different for strap- The undesired modes may be greatly suppressed in accordance with this arrangement because a discontinuity exists for each suchundesired mode. To maintain operation in a single undesired mode, the frequency would necessarily alternate between relatively widely separated values. However, even this technique is not fully effective under all conditions and improved stabilization is desirable or required for certain magnetron operations.

Accordingly, it is a principal object of my invention to V achieve improved mode and frequency stabilization in thereof in different singlet modes necessarily entails oporation at different frequencies since the wave length of the energy produced is determined by the phase relationship between anode tips. In the case of doublet anode modes, the magnetron may operate at slightly different frequencie in the same electronic modes since the phase shift-per-anode-vane is nearly the same in both cases.

Magnetron devices providing high output power at high frequencies have found widespread use for many purposes and in certain of such uses, the load conditions vary widely. In various functions of a magnetron under such varying load conditions, it is important that the magnetron have frequency stability and consequently,

also mode stability. Since magnetrons during operation magnetron operation, particularly in the pi-mode of operation.

In a magnetron structure wherein the anode is continuous,'uniform and re-entrant, it will be resonant at frequencies-for which it is an integral number of wavelengths long at the operating frequency. The phase velocity of the wave of electromagnetic energy will be constant and for each mode, the instantaneous phase difference in potential between adjacent vanes will be uniform around the anode although the phase-shift-peranode-vane at different modes will be different. Power can be generated at each of the mode frequencies. However, the tendency of the magnetron to operate in a single desired mode and at a singlefrequency may be greatly increased in magnetron structures wherein the anode line comprises a series of effective lines having diiferent frequency to phase-shift-per-anode-vane characteritsics for all modes except the desired mode of operation of the magnetron. This is done by establishing a wide separation in frequencies of operation between different portions of the anode.

In accordance with one embodiment of my invention different portions of the anode are strapped and the straps along the different anode portions are positioned at different radii to control the strap lengths and the extent or, in other words, the effectiveness of strapping. The straps at lower radius are more effective in strapping the vanes than straps at a larger radius. The effect of such an arrangement is to establish different frequency versus phase-shift-per-anode-vane characteristics of the different anode portions. At a certain preselected, desired frequency, the phase shift of the electromagnetic wave per unit length of magnetron anode is the same over both portions of the anode and at other frequencies, the phaseshift-per-anode-vane characteristics over the different portions of the anode are different whereby the desired mode is uniformly propagated along all such portions while the undesired modes are propagated non-uniformly, are presented discontinuities and are impeded.

In accordance with another embodiment of my invention, an anode is strapped over only a portion of its circumference and each strap connection is modified by a construction effective to introduce a capacitance in the Patented Mar. 30, 1965.

' istrapping connectionswhic r f ai /dies;

h has the effect of producing a' greater variation in frequency to phase-'shift-per-anodej vane characteristics of the anode; By proper proportion- 3 ingof elements, the.anode'.;linernay again be uniform 1 ,and'continuous for thedesired mode of operationand non-uniform anddiscOntinuousfQrundesired modes,,to stfonglyfavor operation inithe desired 'm'oden. v

In accordancewith another embodiment of my inven-,

- tion'a magnetron anodeis strapped along a portion of its periphery. in a capacitive manner whereinalternate vanes: 7 Q are, interconnected and additibnallypa pair of conductive rings are mounted in proximity to the respectiyestraps to establish a capacitive coupling betweenthe' rings'and the closely disp osedstraps. The effect of such an arrange- 1 .ment is to establish a greater variation in frequency of operation at 'diiferent valuesof frequency to'phase-shiftper-anode-vane characteristics of'the anode.

In acco'rdance. with another embodiment of -my invention, strapping is provided along only 'a-portion of the anode but 'along other portions thereof, the spacing be- 7 tween anode segments is increased and the segments themselves are made thicker .or, in other words, of greater circumferential dimension. T he effect of such an arrangement is again to control the phase velocity and frequency yersus phase-shift-per-anode-vane characteristic along the different portions of the anode whereby desired modes are presented regions of'uniform phase velocity'and are uniformly propagated and undesired mode s are Presentedregions of non-uniform phase velocity and are impeded in their propagation.

In accordance with still another embodiment of'tmy' invention, strapping is provided around the entire circum ference of the magnetron anode but along aportion of increased and the segments themselves are'e nlarged in phase-shift-per-anode vane ofthe wave alongthis portion this characteristic is differentfor unwanted modes whereunwanted modes. 7

the curves of FIGURES:14j and 1 5,

FIGURE 10 is a graph showing thetsuperposition of "the'curv'esshown in FIGURES s and .9,

FIGURE ll is atop view of a "agnetron' anode block according to another embodiment of my invention wherev 'in straps are provided.albng a portion of the periphery *of the anode and capacitiverings-radially" spaced from the straps introduce uniform capacitancebetween strapped V segments, g V FIGURE '12'is a viewtalgenalong section12 12of 1 FIGURE 11, V FIGURE 13 is a View taken along section13f=13 of FIGURE 11,

1 FIGURE 13A "is a] partial viewtak enlalong section I 13A,1 3A of FIGURE llgshowing insulating supporting member for a capacitive conductor,

g FIGURE 14' is a graph s'howing a lot of the requenc of a high frequency wave versus its phase-shift-per-anodevane along the unstrapped portion ofjth'e 'anodeshown'in FIGURES 11 and 112, v V

FIGURE -15pis graphphowing a plot of the frequency of the high frequency wave versus its phase-shiftper-anode-vane-along the strapped portion of the magnetron anode shown in FIGURES 1 1 'and 12,

1 'FIGURE 16 is a graph showing'the superposition of j FIGURE 17 is a top view of a magnetron" anode according to another embodiment of my invention wherein strapping is provided alonga fraction 'of the-anode cir- .cumference and along anothe'rportion the intervane spacing and vane'iihicknesse's' are increased,

, theanode, the spacingv between the anodese grnentsi is circumferential dimension to alter the phase velocity and.

- FIGURE 18 is a graph showinga plot of the frequency of the high frequency wave' versus its 'phase-shift-peranode-vane along the strapped portion of the anode shown in FIGURE 17,

- of the anode. The phaseyelocity along the entire anode,

' however, is the'sarne for a wave of'the desired mode while 4 While the specification concludes with claimsparticuing to' one embodimentof my'in'vention, FIGURE 3 is a'graph showing a plot of the frequency- .of the high frequency wave versus its phase-shift-peranode-vane along one strappedportion .of the. anode shown in FIGURES 1 and 2, t V

FIGURE 4 is a graph showing a plot of the frequency of a'high frequency wave versus its phase-shift-per-anodethe magnetron vane along another strapped portion of anode shown in FIGURES l and 2, v

FIGURE 5 is a graph showing the superposition of the curves ofFIGURES 3 and 4,

accompanying 7 FIGURE 17,

' the curves of FIGURES 1 8 and 1 9, t FIGURE 21 isla top'view of an anode block accord- FIGURE 19 is &' graph'showing a plot of the'frequency of a high frequency wave versus its phase-shift-per-anodevane along the unstrapped portion of the anode shown in FIGURE 20 is, a curve showing the superposition of ing to another embodiment of my inventionshowing conductive strapping of the entire anodebut wherein along one portion ofthe anode the intervanespacing and vane vthicknessesa're increased, I

FIGURE 22 is a graph showing a plot'of-the frequency of a high frequency wave versus its phase-shift-per-anodevane along the portion of theanode block having relatively small intervane' spacings,- 1

FIGURE 23 isla graph showing a plot of the frequency of a high frequency wave'versus its phase-shift-peranode-vane along the portion ofthe anode having relatively large intervane spacings, and

FIGURE 24 is a graph showing the superposition of J the curves of FIGURES 22mm 23.

Referring now to FIGURE 1 of the drawings, 1 represents generally an entire magnetron structure embodying an anodeZ according to my invention, the details of which are shown better in FIGURE 2 ofthe drawings.

' The anode 2 comprises a blockof conductive material FIGURE 6 is a top view of an alternative embodiment .ofmagnetronanode according to my invention wherein capacitive strapping of anode vanes is established along a portion of the anode, i V J FIGURE 7 is a view taken along section 7-7 of FIGURE 6,

. FIGURE 8 isja graphshowing a plot of the frequency I .of a high frequency wave .versus its phase-shift-per-anode- .vane along the unstrapped portion of the anode shown in FIGURES 6 and 7,,

FIGURE '9 is a graph showing a' plot of the frequency such as: copper and is enclosed'in a chamber formed by a peripheral ring 3 and respective end plates 4 and 5 connected at their outer'peripheries, to the ring 3. Anode .bl-ockf2 is provided with a circular aperture centrally thereof and a plurality of cavities formed by a plurality of vanes at 6, 7, 8, 9, 10, 11, 12 and 13extending radially inwardly from the ring 3 as shown more clearly in FIG- URE 2 of the drawings. Plate 5 is centrally apertured and flanged at 14 to accommodate and support a post 15 on which is mounted a cathode represented in its entirety at 16, disposed in the central aperture of anode 2. The cathode is of a smaller radius than the anode aper= am ss ture to establish an annular interaction region 17 between the cathode and inner tips of the adjacent anode Cathode 16 includes a hollow thirrible shaped member 18 apertured at 19 to establish convection communica-,

tion withthe interiorof the magnetron. A pair of out- 'wardly projecting rings. 20 and 21 are secured near respeetive ends of member 18 and are provided with axially.

strap '56 passes through groove 59 invane 9 in similar I a conductive strap interconnecting vanes 7 and 9, 57a

is a conductivestrap interconnecting vanes 9 and 11.

Eachof the straps 55, 5 6, 57 and 57a is capacitively coupled to the vane which is intermediate to the vanes to which it is connected. Thus, strap 55 passes through a groove 58 invane 7 in relative close proximity thereto,

. manner, strap 57 passes through groove 60 in vane 23, and

aligned notches to accommodate insulating columns 22.

ture of copious electron emission, a resistive wire24' responsive toan electrical current for producing heat is wound spirally about the columns 22 as a group. The

electrons emitted by surface 23 are axially confined in lishing mechanical and electrical insulating support for the member 27, a hollow, frustro-conical ceramic memberlat) has one end secured in abutment with flange 29 and its other end in abutment with a radial, inward flange 31 of a tubular member secured to flange 14. For imparting rigidity and support to the flange 31, a ceramic ring 32 is secured to the flange on the side of it opposite to member 30. For establishing external electrical connections to the ends of heater Wire 24, an annular flanged conductive member 33 forming one external terminahis supported in insulated relationship to member 27 by an annular insulator 34 secured to members 27 and 33 and a flanged, tubular, conductive member 35 is supported in insulated relation to member 33 by an annular insulator 36. The ends of the heater wire are connected to these members as shown. .The junction of member 35 to the insulator 36 is strengthened by an annular insulator 37 secured to the side of the flange remote from insulator 36. A tubulation 38 is secured to the exterior end of member 35 by connection between a folded-back flange 39 of the'tubulation and the inner part of the member 35. Although shown broken away, the tubulation which facilitates evacuation of the interior of the magnetron is hermetically sealed after such evacuation.

For providing an output line for the magnetron, a coaxial line 49 is provided and includes an outer conductor 41 and an inner conductor 42. Outer conductor 41 is disposed in the aperture of plate 4 and is secured thereto. For mounting inner conductor 42 centrally along the interior of conductor 41, a flanged thimble shaped supporting member 43 and a flanged tubular member 44 with a rigid, hollow, frustro-conical insulator 45 in abutment with the flanges of these members are provided. Rigidity and strength is imparted to the structure by ceramic insulators 46 and 47 bonded on the sides of the flanges 0pposite to the ends of member 45. The inner conductor 42 is connected to a point on one end of vane 7 of the magnetron anode block through a line 43 to facilitate conduction of output power from the magnetron.

.s trap 57a passes through groove 59a in vane 10. These 7 straps establish strapping over one-half of the magnetron anode circumference and along the other half of the magnetron circumference, a group of 4 straps, 61, 62, 63 and 63a interconnect respective pairs of vanes and 12,

i 11 and '13, 12 and 6 and Band 7. These respective straps are accom'rnoda ted by grooves 64 in vane 11, 65 in vane 12, 66 invane 13 and 66a in vane 6. In each of these cases the strap is in relative close proximity to the vane having the groove for accommodating the strap so as to establish a capacitive coupling between this vane and the two vanes to which the strap is directly connected.

'In accordance with a feature of my invention, the straps 61, 62, 63 and 63a are disposed at a greater radius from the magnetron axis than the corresponding straps 55, 56, 57 and 57a. Also the grooves 64, 65, 66 and 66a are wider than grooves 58, 59, 6t) and 59a so that the capacitive coupling between these and the vanes through which they pass is decreased. In accordance with known magnetron principles, the efiect of strapping a magnetron along a greater radius is to lessen the effectiveness of such strapping. That is, the greater the radius at which the straps are positioned, the lower the coupling between the pling between adjacent cavities.

vanes to which they are attached and the lower the cou- Accordingly, the char- "acteristics of [frequency versus phase-shift-per-anode-vane are different along thejrespective halves of the magnetron anode. This is represented by the curves67 and 68 in FIGURES 3 and 4 respectively, of the drawing In FIGURES 3. and 4 the ordinates represent the frequency of a wave propagated along the magnetron anode anode-vane of pi-radians than that of curve 68. In FIG- A direct magnetic field is established axially along the interaction region by opposed electromagnets 4S and 50 URE 5 the curves 67 and 68 are superimposed and it is to be observed that the curves have points of intersection 69 and 7t). Accordingly, an electromagnetic wave of frequency f and a phase-shift-per-anode-vane of 37r/ 4 corresponding to the point 69 is propagated with equal velocity along the two halves of the magnetron anode. The point 70 is a space harmonic of this wave and has a phase shift-per-anode-vane of 51r/4. At each other value of phase-shift-per-anode-vane, the frequency of operation along the magnetron halves is different as observed by the spacing of the waves 69 and 76. Thus, electromagnetic waves at these frequencies and values of phase-shift-peranode-vane are impeded and not propagated uniformly about the anode.

It is to be noted that in accordance with my invention the magnetron may be made to operate with stability at a number of different frequencies which are determinable by the points of intersection of curves such as 67 and 68.

Also, it should be observed that the shape of curves 67 and 63 is aifected by the vane strapping and in particular by the radial position of thestraps along the magnetron anode. Thus, in accordance with this feature of my invention, the frequency of stable operation of a magnetron may be readily controlled and curves 67 and 68 may be made to coincide at several dif erent values of phase-shiftper-anode-vane at which a wave may be propagated about the magnetron anode.

Referring now to FIGURE 6 of the drawing illustrat- 7 operation. 'phase shift of 31r/ 4 an electromagnetic wave will propaf lentire' magnetron anode similar to the anode 2 shown in "ing another embodiment of my invention, 71represents an rronans l-sand 2 and having'vanesj72 through '79. A

ferentially to another point within groove 81. members 180 YandSZ fare inoverlapping-relationand spaced 1 from each, otherso-as to'establish a capacitive couplin'g 'theretietween. I Also each of these strapsfisin spaced,,butl proximate relation to. thevane73 to alsoest'abiish capaci tive coupling between eachof thevanes 72 and 74 and thevane 73. In a similar manner a pair'fof strap members 83 and84 extend respectively from vanes 73 and 75 to points within groove85'in vanev 74' and ar'etjiri overlapping relation :with' respectto each other so'as to establish 1 capacitive coupling betweenvanes 73 and 74, 73 and 7 5, V

"ping is provided between the portion jofth e anode from vane 92jclockwis to fvane 100 by, a plurality ofrstrapped" egments'numbered' 117, 118,

119, 120 and IZIeXtendingaIongarcuate portions of the same circle and being spaced 'circumferentially from "each foth er. Theselsegments are. connected respectively to vanes92,. 94; 956,98fand ltltlias represented by the enf' large'd dots showntat 122,123; 124, IZS'andIZSQ. The

interconnectionbetween strapelement jand vanes and the relationship between strapped segments is' shown more a clearly. in FIGURE 13 offlthejdrawingsl representing a "ofEIGURE; 11. 'In

yiewi taken' along section thisfigure it is observed that-tires a'p elements-are axially spaced butin relativelyclose proximityto the'ivanes of the magnetron to which they .arelnot connected to estab- "lishasignificantcapacitance therebet-weenl I In accordance with another featureofthisernbodiment 1 of-imy invention,' the capacitancefbetween any one strap element and otherstrap'elements along the circle of the and 74and 75. ,Theportion of the magnetron extending 1 circumferentially from vane 75 clockwise to vane .72 -is 'unstrapped.

and the abscissas represent the phase-shift-peranode-vane of the wave aboutthemagnetron anode. The curve 86 in FIGURE 8 'representsthe propagation characteristics along the unstrapped p ortionslof anode 71Iand thecurve 87 in FIGURE 9 represents the propagation -characteristics alongthe strapped portion. It isfto -be 'observed from curve 87 that in this'ernbodiment of myinvention, the effect of the capacitive strapping is to makethe curve 7 I The propagationcharacteristics of-the respective un strapped and strapped portions of the magnetron anode 71 aretshownin' FIGURES 8,and,9, respectively. In

same radius is' increased'byfa conductive arcuate member jextending'in close proximity to each of the. strapped ele ments and preferably along the arcof acircle concentric "with that of the strapped element's. Thus; the conductive member 127 extends from a point; above-vane 91 arcuately to apoint above vane 99 so as m be circumferentially coextensive withthestrapped arrangement including straps 107 through 111'. The close spacing" between member 127 and each of these, strapped segments establishes a capaci FIGURES .8 and 9 the. ordinates represent the frequency For an electromagnetic wavepropagated along "theanode tive coupling between thememb'er an d-each of these seg- "ments' andtherefor also between anyfone'of these segments and any one other of these segments. Similarly, conductive member 128jextends from a point above vane '92 .to apoint above vane ltltlso as to be in proximity to and; circumferentially v coextensive with; the strap elements 117fthroughd2 1} 'The conductive members 127 '1 jan'd 128 may be supported. in axially spaced relation to- .ggthe vanes by insulating members as shown at1129 and of propagation characteristics peaked. As shown in FIG- URE 10 of the drawings, illustrating the superposition of curves 86 and 87,points of coincidence 8 8and 8 of the curves establish values of 'frequency and ,phase shift-per anode-vane at which the magnetron would be stable in That is to say, that for frequency f and a gate uniformally about the magnetron anode. A space *harmonic at this same frequency would bepropagated at a phase-shift-per-anode-vane of 51r/4. 'At all'othertfre quencie's the magnetron anode 71 presents discontinuities and these frequencies are not uniformly propagated so as to interact favorably with the beam. Accordingly, this "embodiment of my invention comprises an alternate arrangement for providing modestabilization of the magnetronanode. p1 I In accordance with another embodimentof my invention shown in FIGURE 11' of the drawings, enhanced capacitive coupling betweenvanes may be achieved to v produce an even sharper peak of the curve of frequency 134 between member 127 and respective vanes 92 and 98 and insulating members 131 and 132' disposed between member .128 and vanes 93 and 99, respectively. These insulating members'are shown in FIGURE 11 andv insulator 129 is shown in detail in FIGURE,1'3A.;- j

In accordance with the invention shown in FIGURE 11 of the drawing the portion of the anode 1 which is unstrapped has a frequency versus phase-shift per-anodelyane propagating characteristic as shown at 133 in FIG- URE 14 of the drawings'andthe propagating characteristic along'the strapped portion of the anode is as shown at 134 in FIGURE 15 of the drawings; In each of these figures 'the ordinate represents the frequency of the propagated wave while theabscissa represents'the ,phase-shift- V 'per-anode -vane. It shouldbe observed that by reason of theincreased capacitance between strapped elements es- -tablishedfby the conductive members 127 and 128, the

curve134 is more peaked thancurve 87 shown in FIG- URE 9 of the drawings and thus, the strapping arrange- "ment of FIGURE 11 is advantageous in' providing inversus phase-shift-per-anode-vane characteristic, In FIG- URE 11, the anode is'provided with sixteen vanes numbered consecutively from 91through 1%. In accordance with a featureof this embodiment of my invention,

the portion of the. anode from vane 91c1ockwise-to vane $39 is provided with a plurality of arcuate strap elements 107, 108, 109, and llll'textending along arcs of the same circle; :The strap elements are circumferentially spaced from each other'and successive ones are connected to alternate vanes as represented by the'solid enlarged' dots 112,113, 114, and 116 connecting strap elements 107, 108, 109 114 and 111 to-respective-vanes' 91, 93;

the different strap elements along anode. v

In a manner similar to that described, capacitive strapcreased capacitive strapping in situations wherein it is desirable.- 1 i a j V In FIGURE 16 is shown thesupe rposition of curves 133 and 134, At point 135 these curves intersectto designate a a frequency fi andphase-shifflper-anode-vane of 31r/ 4 at which therespective strapped and unstrapped portions of V lthe'magnetron anode propagate with equal facility. That V 70' 95, 97 and 99; The respective strap elements terminate 4 above the'vane located between the vanes connected to this portion of the a is to say th'e electromagnetic wave having the frequency fg and being propagated inthe mode of 31r/4 radians per -vane is propagated uninhibited around the magnetron anode while all other frequencies are presented discontinuities and therefore are greatly inhibited. A space 'ha'rmonic' is also readily propagated at frequency f indicated by the intersection of-these curves at 136 but which has a phase-shift-per-anode-vane of 51r/ 4 radians.

In accordance with stillanother embodiment of my invention as shown in FIGURE 17' of the drawings,'a magnetron anode represented generally at 137 is provided alternate vanes along the 9 with a plurality of vanes such as shown at 138, 139, 140 and 141 which are of substantially the same dimensions and spaced uniform distances d over a portion of the circumference of the anode and a pair of further vanes 142 and 143 are provided along the remaining portion of the anode circumference. In accordance with a feature of my invention the vanes 142 and 143 are circumferentially spaced from each other at a distance d substantially twice the spacing of the vanes 138 and 139 from each other. Also, the thickness of each of the vanes 142 and 143 is substantially twice the thickness of any of the vanes 138 through 141. Along the portion of the anode having the narrow vanes 138 through 141, a conventional strapping arrangement is provided by a pair of straps 144 and 145 interconnecting respective pairs of vanes 138 and 140, 139 and 141. Appropriate grooves 146' and 147 in respective vanes 139 and 140 are provided to accommodate the respective straps 144 and 145.

'In accordance with this embodiment of my invention, the propagation characteristics of an electromagnetic wave traveling along the portion of the anode having the strapped vanes is represented by the curve 148 in FIG- URE 18 of the drawings wherein'the ordinate represents the frequency of the wave and the abscissa represents the phase-shift-per-anode-vane along this portion. It is observed from this curve that it represents a conventional condition of strapping wherein thecurve is depressed at a phase-shift-per-anode-vane of 1r radians and is peaked at phase shift values between zero and 1r radians and between 11- and 21:- radians.

As shown in FIGURE 19 of the drawings, the propagation characteristics of an electromagnetic wave along the portion of the anode having enlarged vanes subtending angles twice as large as the angles subtended by vanes along the strapped portion and the spacings is as represented by the curve 149 and wherein the ordinate represents the frequency of the wave and the abscissa represents the phase-shift-pe r-anode-vane along this second portion. It is observed that in this figure of the drawings the curve is peaked at a value of 1r and 31r radians phase shift-per-anode-vane. 1

In FIGURE 20 of the drawings the curves 148 and 149 have been superimposed using the ,Bd scale for the abscissa at the points 150 and 151. Since the phase shift of the electromagnetic wave per unit length around the strapped portion of the magnetron is the same as that along the unstrapped portion, the phase shift of the wave is twice as great along the unstrapped portion as it is along the strapped portion. Thus, in the superimposed positions in FIGURE 20 curve 149 is shown for 411' radians on the fid scale while the curve 148 is shown for merely 21r r'adians on the [3:1 scale. At point 150, an electromagnetic wave of frequency f and having a phase-shift-peranode-vane along the strapped portion of the anode equal to 31r/4radians and a phase-shift-per-anode-vane f'61r/ 4 radians along the unstrapped portion of the anode is propagated uninhibited. That is, this wave is presented no discontinuity and travels with equal facility alongeach section of the anode. Also, a space. harmonic of this wave at the same frequency and having a phase shift per vane of 57T/4 radians represented by the point 151may also be propagateduninhibited along the magnetron anode. At all other frequencies which are space harmonics of frequency 72; the electromagnetic waves are presented discontinuities about the magnetron anode and therefore are not propagated.

In accordance with still another embodiment of my invention shown in FIGURE 21. of the drawings, the magnetron anode as represented at 152 may be constructed asis the anode 137 in FIGURE 17 of the drawings with the addition of straps along the portion of the anode which is unstrapped in FIGURE 17. Thus, the anode 152 is provided with vanes 153, 154, 155 and 156 of predetermined thickness and adjacent spacing ti, and with additional vanes 157 and 158 which are spaced from each other a distance d substantially twice the intervane spacing of vanes 153 and 154, for example, and each of the vanes 157 and 158 is substantially twice as thick in a circumferential direction as any one of the vanes 153 through 156. The entire anode block is strapped by straps 159, 160 and 161 disposed along one radius and interconnecting respective pairs of vanes 153 and 155, 155 and 157, and 157 and 163. Also, straps 162,163 and 164 disposed at another radius are provided to interconnect respective pairs of vanes 158 and 154, 154 and 156, and 156 and 158, respectively.

FIGURES 22 and 23 represent the propagation characteristics of electromagnetic waves along the respective portions of anode 152 from vane 153 to vane 156 and from vane 157 to vane 158, both taken in a clockwise direction in FIGURE 21. Inthese figures the ordinate represents the frequency of an electromagnetic wave and the abscissa represents the phase-shift-per-anode-vane. In FIGURE 22 the curve 165 shows that the propagation characteristics along the narrow vane portion of the anode is very peaked at values between zero and 11' radians and between 1r and 2vr radians and in FIGURE 23 the curve 166 shows that the propagation characteristics along the wide vane portion of the anode is considerably less peaked between zero and 11" and between 11' and 211' radians. In FIGURE 24, the curves 165 and 166 are superimposed on the same scale and intersect at the points 167 and 168 at each of which the propagation characteristics along the respective portions of the anode are the same. Thus, at a frequency f corresponding to these points waves having phase-shifts-per-anode-vane of approximately 41r/3 or 81 3 radians per vane distance d arepropagated with equal facility and uninhibited about the entire magnetron anode. At other frequencies which are not space harmonics of this frequency the electromagnetic waves are not propagated uniformly.

It is also within the purview of my invention to provide a magnetron anode as shown in either of FIGURES 17 or 21 of the drawings but without any straps between any of the vanes. In such an embodiment, the intervane spacings and vane widths would be uniform along one portion of the anode to establish a first propagating characteristic of frequency versus phase-shift-per-anodevane and along the other portion of the anode a second propagating characteristic of frequency versus phaseshift-per-anode-vane is established. The characteristics may be so interrelated as to have a pair of values of frequency and pha se-shift-per-anode-vane which are the same for each portion to support propagation of a wave around the entire anode at these values and to inhibit propagation of waves at all other values except space harmonics. Thus, mode stabilization may again be achieved in accordance with this technique.

While the present invention has been described by reference to particular embodiment thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the invention. I, therefore, aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A magnetron anode comprising a hollow conductive structure having a plurality of spaced conductive segments extending inwardly from the inner wall of said structure defining an anode circuit between each adjacent pair of segments, means providing an electron beam adjacent the ends of said conducting segments including means subjecting said beam to crossed electric and magnetic fields to establish motion of said electron beam to provide high frequency excitation of said anode structure, means including conductive members establishing a predetermined capacitive coupling between alternate segments along a portion of said anode to provide a predetermined frequency versus phase shift per anode segf 7 it merit characteristic for said portion of said means including conductive members'establishing anelectrical coupling different from said predetermined'cou pling between alternate'segments along another portion of .said anode to provide a different frequency versus phase shift peranode segment characteristic which, in-

7 tersectssaid first-characteristic so thatstable operation is attained for a frequency corresponding 'to the intersection of said frequency versus phase shift per anode segment characteristics, each of said anode portions in .cluding at least two adjacent. anode circuits.

2. A magnetronanodecomprising a hollow conductive structure having a plurality of 'convergent conductive segments extendingiinwardly from the inner wall of said structure defining an anode circuit between eachadjacent pair of segments, means providing an electronbeam adjacent the ends of said conducting segments including means subjecting said'beam to crossed electric and magnetic fields to'establish motion of said electron beam to provide high frequency excitation of said anode structure, means including conductive members establishing 'a predetermined capacitive coupling between alternate segments along a portion of said anode -to provide a predetermined frequency versus phase shift per anode segmentcharacteristic for said portion of said anode and means including conductive members establishing an electrical coupling different from said predetermined coupling between alternate segments along another portion of said anode'to'provide a different frequency versus phase shift per anodesegment characteristic which intersects said first characteristic so thatstable operation is attained for a frequency corresponding to the intersection of said frequency rversus phase'shift per anode segment characteristics, each of said anode portions including at least two adjacent anode circuits.

I I 1 3, A magnetron anode comprising a hollow conductive structure having a plurality of spaced conductive segments extending inwardly from the inner Wall'of said structure, means establishing a predetermined electrical coupling between alternate segments along a portion of e 1 said anode and including a pair of conductive members assoc ated with three successive onesofsaid segments,

the first of said pair of conductive members being directly connected only to the first of said successivesegments the second of said pair of conductivemembers being directly connected only to the thirdof saidsuccessive segments, said pair of conductive members extenda ing across the spaces between said successive segments inanode v and v per' anode segment characteristic for said portion of said anode, said means including conductive members connected to respective ones of said alternate segments and being in spaced proximate overlap'ping relation with each other and further being in spaced proximate relation to the segment between said alternate segments along a portion of said anode the remaining portion ofsaid anode having a different coupling betweensaid anode segments to provide a different frequency versus phase shift for anode segment characteristic which intersects 'said first characteristic so that stable operation is attained for a frequency corresponding to the intersection of said fre:

q'uency versus phase shift per anode segment characteristics, each of said anode portions including at least two adjacentanode circuits. e I

'6. A magnetron anode comprising a hollow conductive structure having first and second pluralities'of convergentpconductive segments of uniform length extending inwardly from the inner wall of said structure defining an anode'circuit between each adjacent. pair of segments, means providing an electron beam adjacent the ends of said conducting segmentsincluding means subjecting said beam to crossed electric and magnetic fields to establish motion of said electron beam to provide high 7 i other portion being of a value diiferent from said second predetermined value, andconductive means interconnecting alternate segments along said one portion and 1 establishing a'capacitive coupling therebetween' and coof said conductive members between said interconnected Y alternate segments for introducing acapacitance in said conductive connections. a r

5, A magnetron anode comprising a hollow circular,

conductive structure having a plurality of convergent, conductivev segments extending inwardly from the inner wallof said structure defining ananode circuit between each adjacent pair of segments, means providing an.-electron beam adjacent the ends of said conducting segments includingmeans subjecting said beamto crossed electric and magnetic fields to establish motion of said'electron' beam to provide high frequency excitation of said anode structure, means establishing a predetermined vcapacitive coupling between alternate segments along a portion of said anode and between'each of saidalternate segments and the segments'therebetween and cooperating therewith to provide a predetermined frequency versus phase'shift operating therewith to provide a predetermined frequency versus phase shift per anode. segment characteristic for said one 'portionfofsaid anode, said other portion of said anode having a different coupling between'said anode segments to provide a difierent'frequency. versus phase shift per anode segment characteristic which, intersects said first characteristic so'that stable operation is attained for a frequency corresponding to the intersection of said frequency versus phase shift per anode segment characteristics, each of said anode portions including at least 'two adjacent anode circuits.

7. A magnetron anode comprising a hollow conductive structure having a plurality of convergent conductive segments of uniform length extending inwardly from the inner wall of said structure, definingv an anode circuit between each adjacent pair of segments, means providing an electron beamadjacentthe ends of said conducting segments including means subjecting said beam to crossed electric and magnetic fields'to establish motion of said electron beam to provide high frequency excitation of said anode structure, the segments along a portion of said anode being of a substantially uniform predetermined thickness and adjacent segments along said portion being of apIedeteImined spacing, the segments along another portion of said anode having a thickness I 'for a frequency corresponding to the'intersection o'f'said frequency versus phase shift per anode segment charac- '13 teristics, each of said anode portions including at least two adjacent anode circuits.

8. A magnetron anode comprising a hollow conductive member having a plurality of convergent conductive segments of substantially uniform length extending inwardly from the inner Wall of said structure, defining an anode circuit between each adjacent pair of segments, means providing an electron beam adjacent the ends of said conducting segments including means subjecting said beam to crossed electric and magnetic fields to establish motion of said electron beam to provide high frequency excitation of said anode structure, the segments along a portion of said anode being of a substantially uniform predetermined thickness and adjacent segments along said portion being of a predetermined spacing, the segments along another portion of said anode having a thickness substantially twice said predetermined thickness and the spacing between adjacent segments along said other portion being substantially twice said predetermined spacing, and means establishing a capacitive coupling between alternate segments of said anode said different portions of said anode having different frequency versus phase shift per anode segment characteristics which intersect so that stable operation is attained for a frequency corresponding to the intersection of said frequency versus phase shift per anode segment characteristics, each of said anode portions including at least two adjacent anode circuits.

9. A magnetron anode comprising a hollow conductive member having a plurality of spaced, conductive segments extending inwardly from the inner wall of said structure, means establishing an electrical coupling between alternate segments along a portion of said anode and including a plurality of coplanar conductive members, one of said members being connected to each of said segments and terminating in spaced proximity to each of the segments adjacent thereto, the plane of said members being transverse to the axis of said anode, further conductive means coplanar with said members and disposed in spaced proximity to each of said first mentioned conductive means for establishing a capacitive coupling between alternate segments along said portion of said anode.

10. A magnetron anode comprising a hollow conductive member having a plurality of convergent, conductive segments extending inwardly from the inner wall of said structure, means establishing an electrical coupling between alternate segments along a portion of said anode ments, a first conductor coplanar with said members and disposed in spaced relationship with each of said first plurality of conductive members for establishing a capacitive coupling between each of said first plurality of conductive members and each other thereof, a second conductor coplanar with said members and extending in spaced proximity to said second plurality of conductive members for establishing a capacitive coupling between each of said second plurality of conductive members and each other thereof.

11. A magnetron device comprising an anode structure including a plurality of spaced conductive anode segments joined at one end to a conducting structure defining an anode circuit between each adjacent pair of segments, means providing an electron beam adjacent the opposite ends of said conducting segments including means subjecting said beam to crossed electric and magnetic fields to establish motion of said electron beam to provide high frequency excitation of said anode structure, conductive means connected to alternate anode segments establishing capacitive coupling over one portion of said anode and cooperating therewith to provide a predetermined frequency versus phase shift per anode segment characteristic for said portion of said anode, the remaining portion of said anode having a different coupling between said anode segments to provide a different frequency versus phase shift per anode segment characteristic which intersects said first characteristic so that stable operation is attained for a frequency corresponding to the intersection of said frequency versus phase shift per anode segment characteristics, each of said anode portions including at least two adjacent anode circuits.

12. A magnetron device comprising an anode structure including a plurality of spaced radially conductive anode segments joined at one end to a surrounding conducting structure defining a central opening at the opposite ends thereof, said anode structure further defining an anode circuit between each adjacent pair of segments, means providing an electron beam adjacent the inner ends of said conducting segments including means subjecting said beam to crossed electric and magnetic fields to establish motion of said electron beam to provide high frequency excitation of said anode structure, conductive means connected to alternate anode segments establishing capaci tive coupling over one portion of said anode and cooperating therewith to provide a predetermined frequency versus phase shift per anode segment characteristic for said portion of said anode, a second portion of said anode having a different coupling between said anode segments to provide a different frequency versus phase shift per anode segment characteristic which intersects said first characteristic at equally spaced points on opposite sides of 1: radians phase shift per anode segment so that stable operation is attained for a frequency corresponding to the intersections of said frequency versus phase shift per anode segment characteristics. 7

References Cited by the Examiner UNITED STATES PATENTS GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS, Examiners. 

11. A MAGNETRON DEVICE COMPRISING AN ANODE STRUCTURE INCLUDING A PLURALITY OF SPACED CONDUCTIVE ANODE SEGMENTS JOINED AT ONE END TO A CONDUCTING STRUCTURE DEFINING AN ANODE CIRCUIT BETWEEN EACH ADJACENT PAIR OF SEGMENTS, MEANS PROVIDING AN ELECTRON BEAM ADJACENT THE OPPOSITE ENDS OF SAID CONDUCTING SEGMENTS INCLUDING MEANS SUBJECTING SAID BEAM TO CROSSED ELECTRIC AND MAGNETIC FIELDS TO ESTABLISH MOTION OF SAID ELECTRON BEAM TO PROVIDE HIGH FREQUENCY EXCITATION OF SAID ANODE STRUCTURE, CONDUCTIVE MEANS CONNECTED TO ALTERNATE ANODE SEGMENTS ESTABLISHING CAPCITIVE COUPLING OVER ONE PORTION OF SAID ANODE AND COOPERATING THEREWITH TO PROVIDE A PREDETERMINED FREQUENCY VERSUS PHASE SHIFT PER ANODE SEGMENT CHARACTERISTIC FOR SAID PORTION OF SAID ANODE, THE REMAINING PORTION OF SAID ANODE HAVING A DIFFERENT COUPLING BETWEEN SAID ANODE SEGMENTS TO PROVIDE A DIFFERENT FREQUENCY VERSUS PHASE SHIFT PER ANODE SEGMENT CHARACTERISTIC WHICH INTERSECTS SAID FIRST CHARACTERISTIC SO THAT STABLE OPERATION IS ATTAINED FOR A FREQUENCY CORRESPONDING TO THE INTERSECTION OF SAID FREQUENCY VERSUS PHASE SHIFT PER ANODE SEGMENT CHARACTERISTICS, EACH OF SAID ANODE PORTIONS INCLUDING AT LEAST TWO ADJACENT ANODE CIRCUITS. 